Materials Data on MgSi2 by Materials Project

Abstract

MgSi2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are three inequivalent Mg sites. In the first Mg site, Mg is bonded in a 5-coordinate geometry to nine Si atoms. There are a spread of Mg–Si bond distances ranging from 2.75–3.07 Å. In the second Mg site, Mg is bonded to six Si atoms to form distorted MgSi6 octahedra that share corners with two equivalent MgSi12 cuboctahedra and edges with two equivalent MgSi6 octahedra. There are two shorter (2.87 Å) and four longer (2.88 Å) Mg–Si bond lengths. In the third Mg site, Mg is bonded to twelve Si atoms to form distorted MgSi12 cuboctahedra that share corners with two equivalent MgSi6 octahedra, edges with four equivalent MgSi12 cuboctahedra, and faces with two equivalent MgSi12 cuboctahedra. The corner-sharing octahedral tilt angles are 22°. There are a spread of Mg–Si bond distances ranging from 2.79–3.12 Å. There are four inequivalent Si sites. In the first Si site, Si is bonded in a 8-coordinate geometry to five Mg and three Si atoms. There are two shorter (2.42 Å) and one longer (2.51 Å) Si–Si bond lengths. In the second Si site, Si is bonded in a 7-coordinate geometry to four Mg and three Si atoms. There are two shorter (2.42 Å) and one longer (2.44 Å) Si–Si bond lengths. In the third Si site, Si is bonded in a 9-coordinate geometry to five Mg and four Si atoms. There are a spread of Si–Si bond distances ranging from 2.51–2.64 Å. In the fourth Si site, Si is bonded in a 8-coordinate geometry to four Mg and four Si atoms.